Shaped filamentary structures and methods of making

Description

[0001] This invention relates to fibrous substrates for the production of carbon and/or ceramic (including mixtures of these) fiber reinforced carbon and/or ceramic (including mixtures of these) composites and to methods of manufacture of same. Exemplary of such a composite is a carbon fiber/carbon matrix brake disk made by depositing a carbon matrix on a carbon fiber substrate of the invention, the fibrous material of the substrate being carbonized to reinforce the carbon matrix with carbon fibers. Deposition of carbon on the substrate is effected by in situ cracking of a carbon bearing gas (hereinafter referred to as carbon vapor deposition, abbreviated "CVD" or carbon vapor infiltration, abbreviated "CVI", as these terms are used interchangeably for purposes of the present invention) or by repeatedly impregnating the substrate with a carbon bearing resin and thereafter charring such resin or a combination of such methods to density the carbon matrix on the carbonized substrate. The invention is not directed to formation of the carbon matrix or densification of the carbon fiber substrate, but rather to the substrate, its preparation, and subsequent densification in known manner to provide a carbon fiber reinforced composite, especially one suitable for use as a friction disk in a brake or clutch.

[0002] A preferred material for use in the invention is polyacrylonitrile (PAN) fiber which, particularly if CVD is to be employed, is preferably in an oxidized condition which facilitates subsequent carbonization. Greige PAN fiber and carbon fiber or graphite fiber may also be found to be suitable. Oxidized PAN fiber (which may hereinafter be referred to as "OPF") is available commercially in various forms, including tows, yarns, woven and non-woven fabrics, knit fabrics and felts. For the present invention, a preferred starting form is OPF tow such as that available from RKT of Muir of Ord, Scotland. Tows and/or yarns of PAN fibers, carbon fibers, graphite fibers, ceramic fibers, precursors of carbon fibers and precursors of ceramic fibers, and mixtures of these may be used. As used herein the term "tow" is used to refer to a strand of continuous filaments. As used herein the term "yarn" is used to refer to a continuous strand of continuous or staple fibers or blends of these; thus the term "yam" encompasses tow. Continuous fiber is generally preferred over discontinuous fiber due to enhanced mechanical properties in the resultant composite product.

[0003] In certain known processes (including those disclosed in U. S. Patent 3,657,061 to Carlson et al., and U.S. -A- 4,790,052 to Olry) for the manufacture of carbon fiber reinforced friction disks, such as brake disks employed on aircraft, annuli are cut out of parallel-sided multi-layered sheets of PAN fiber material to form one or more substrate annuli. This procedure results in considerable wastage of expensive PAN or OPF sheet and the offcut material cannot be reprocessed to continuous filament form to make anew continuous filament sheet.

[0004] According to Lawton et al. U.S. -A- 4,955,123; 5,081,754; 5,113,568; 5,184,387 and 5,323,523, the amount of offcut waste generated in the production of preforms to be used in production of disks for aircraft braking systems is reduced by preparation of a shaped filamentary structure in the following manner: needlepunching a unidirectional layer of filaments to provide a degree of dimensional stability; cutting a plurality of segments from the unidirectional layer of needlepunched material; assembling a plurality of such segments in side-by-side contiguous relationship to produce a filamentary layer of the required structural shape; superposing at least one similar layer on the first layer; and needlepunching the superposed layers to assemble and join the segments. According to Lawton et al., wastage of the fibrous material is reduced because it is possible to lay out the segmental shapes to enable maximum use of filamentary material. This Lawton et al. process has several drawbacks. The needlepunched unidirectional "fabric" layer of filaments and the segments cut therefrom are difficult to handle due to poor lateral dimensional stability of the unidirectional layer of filaments. The arcuate segments cut from the unidirectional layer of filaments must have differing filament to chord angles to provide adequate properties to the annular preform and the resultant friction disk. Considerable offcut waste material is generated because the segments must be cut from the sheet having various chord orientations relative to the direction of the filaments. Arcuate segments having differing filament to chord angles must be assembled so as to provide both radially disposed and chordally disposed filaments relative to the annulus to be formed. This lattermost requirement presents a logistics problem.

[0005] According to U.S. -A- 3,730,320 to Freeder et al., segmented strips of resin impregnated carbon or graphite cloth are assembled in partially overlapping relationship with opposite ends at opposite faces of the disk. The disk is formed and cured under high temperature and pressure to bond the segmented strips together. The cured disk is then pyrolyzed to produce a carbon or graphite char bond matrix.

[0006] According to another known method, arcuate sectors of resin impregnated carbon or graphite cloth are assembled in stacked annular layers with the radial joints formed by the abutted ends of the sectors of each layer being offset circumferentially relative to those of adjacent layers.

[0007] It is an object of certain embodiments of the present invention to minimize off-cut fibrous material when forming fibrous preforms to be used in the manufacture of friction disks.

[0008] It is a further object of certain embodiments of the invention to provide a near net shape annular friction disk preform.

[0009] According to an aspect of the invention there is provided a method of making a multi-layered annular shaped fibrous structure (10, 40) having a radius and a thickness comprising the steps of: forming a multidirectional fabric (30, 50) having filaments (12) extending in at least two directions; cutting arcuate or trapezoidal sectors (20, 20') of an annular shape from said multidirectional fabric, each sector having a radial width (22, 22') generally corresponding to the radial width (24)of the fibrous structure to be formed; assembling the sectors (20, 20') in contiguous relationship to form an annular layer (26) having a radial width (22) generally corresponding to the radial width (24) of the fibrous structure to be formed; providing a stack (29) of thus formed layers of fibrous material, one layer on top of another; and needlepunching the stacked layers (26) to produce cross-linking of the layers by filaments (15) displaced out of the layers (26) and extending in a direction generally perpendicular to the faces (17, 18) of the layers (26).

[0010] According to another aspect of the invention there is provided a flat annular multi-layered fibrous structure (10,40,60,70,80) having a radius and a thickness comprising a stack (29) of layers (26) of fibrous material, one layer on top of another, that are cross-linked to one another by filaments (15) displaced out of the layers (26) so as to extend in a direction generally perpendicular of the faces (17,18) of the layers (26), the layers (26) being formed from arcuate or trapezoidal sectors (20,20') of an annular shape from a multidirectional fabric (30,50) having filaments (12) that extend in at least two directions, each sector having a radial width (22,22') generally corresponding to the radial width (24) of the fibrous structure; the sectors (20,20') being in contiguous or overlapping relationship to form an annular or helical layer (26,41,70,80) having a radial width (22,22',45) generally corresponding to the radial width (24) of the fibrous structure.

[0011] Further embodiments of the invention become evident from dependent claims 2 to 22, and 24 and 25 respectively.

[0012] It is believed that suitable friction disk preforms can be made from various fibrous tapes formed by joinder of arcuate or trapezoidal shaped sectors cut from a multidirectional fabric such as braided, knit, woven and non-woven fabrics, the sectors being needlepunched as they are stacked or coiled layer upon layer.

[0013] The above and other features and advantages of the invention will become more apparent when considered in light of the following description of preferred embodiments of the invention in conjunction with the accompanying drawings which also form a part of the specification.

BRIEF DESCRIPTION OF THE DRAWING

[0014] Figure 1 is an isometric view of a friction disk according to an embodiment of the invention.

[0015] Figure 2 is an enlarged sectional view taken along plane 2-2 of Figure 1, depicting schematically the fiber distribution therein.

[0016] Figure 3 is a schematic depiction showing layout of arcuate sectors to be cut out of a strip or tape of a multidirectional fabric.

[0017] Figure 4 is a plan schematic view of an embodiment of an annular shaped filamentary structure according to the invention formed from a helical tape formed of joined arcuate sectors of a multidirectional fabric.

[0018] Figure 5 is a plan view depicting a layout of arcuate sectors to be cut out from a large strip of of a a multidirectional fabric.

[0019] Figure 6 is an exploded schematic view of an embodiment of an annular shaped filamentary structure according to the invention formed from a pair of helical tapes.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0020] Referring to the drawings, wherein like reference numerals designate like or corresponding parts throughout the several views, there is shown in Figures 1 and 2, a friction disk 10 comprising a stack 29 superposed annular layers 26 formed by joinder of substantially identical arcuate sectors 20 of multidirectional fabric derived from tows 12 of OPF cross-linked to one another by filaments 15 (Figure 2) displaced from layers 26 by needlepunching to consolidate and densify a preform disk similar to preform disk 40 shown in Figure 4, the OPF having been converted to carbon fiber and further densified after needlepunching by carbon matrix deposition using conventional CVI processes. In other embodiments, the cross-linked layers may have deposited thereon a matrix of carbon, ceramic, precursor of carbon, precursor of ceramic, and mixtures of these to further bind together the cross-linked layers. Each annular layer 26 in the embodiment shown in Figures 1 and 2 is formed of six substantially identical arcuate sectors 20 positioned side by side.

[0021] The filaments of tows 12 within the disk 10 may be substantially continuous within each respective arcuate sector 20 between the inside diameter (ID) and outside diameter (OD) cylindrical peripheral surfaces 14, 16 of the disk 10 and its flat, parallel wear faces 17, 18 except those filaments 15 that have been displaced perpendicularly to the wear faces 17, 18 by needlepunching to join the sectors. Continuous fiber (i.e. filament) is generally preferred over discontinuous fiber due to higher mechanical properties in the resultant composite friction disk product.

[0022] The sectors 20, 20' may be cut from a narrow strip such as strip 30 as shown in Figure 3 or a wide sheet such as sheet 50 as shown in Figure 5 and joined end to end or in overlapping manner to form a fibrous layer 26 of the required structural shape which may be joined to another fibrous layer by needlepunching of the stacked layers to form a fibrous preform such as an annular preform disk. Alternatively, the sectors 20, 20' may be joined end to end or in overlapping manner to form a helical fibrous tape (Figures 4, 6, 7, 8) or an annular layer (Figures 1, 2). The helical tape may be arranged to form a flat, hollow annular preform disk having a plurality of fibrous layers such as preform 40 as shown in Figure 4. Sectors 20,20' or a helical tape 41 formed from sectors 20, 20' may be interleaved with an additional helical fibrous tape, formed for example, by collapsing a helical hollow tubular braid as described in U.S.-A-5,217,770 to Morris and Liew. As shown in ghost lines in Figure 6, a helical flat braid tape 61 may be interleaved with helical turns 62 formed of sectors 20 joined end to end or in overlapping manner. The braided helical tape 61 itself may be formed from one or more of side by side parallel braids which may be partially overlapped.

[0023] The fiber volume, i.e., the quantity of fiber per unit volume, which is usually expressed as a percentage with zero percent meaning that no fiber is present and one hundred percent meaning that only fiber is present, is essentially the same throughout each sector and thus any preform or disk formed exclusively from such sectors. In contrast, in preforms and disks formed from needlepunched stacked layers of curved braided filamentary material formed by bending a straight braid, the fiber volume is greater adjacent the inner periphery 14 of disk 10 and adjacent the outer periphery 16 of disk 10, than in the remainder of the disk 10. This variation in fiber volume is a natural result of forming an otherwise uniform straight tubular braid into a flattened annulus or helix. This naturally occurring variation in fiber volume associated with a curved braid formed by bending a straight braid can be minimized by braiding techniques described in U.S.-A-5,217,770 to Morris and Liew.

[0024] Having reference to Figure 3, the sectors 20 having a radial width 22 are cut out from a straight braid 30 having a width 35. Because braid 30 is a multidirectional fabric, as contrasted with a unidirectional fabric as described in the aforementioned patents to Lawton et al., the relative orientation of adjacent sectors is not critical. The ends of adjacent sectors 20 may be contiguous as they are laid out and cut from braid such as braid 30 shown in Figure 3 or tridirectional crosslapped fabric 50 shown in Figure 5. As shown, very little offcut waste is generated compared to known methods, including that shown and described in the above mentioned patents to Lawton et al. Adjacent sectors 20 may be laid out 180 degrees relative to one another. It is also possible to merely cut the multidirectional fabric strip into trapezoidal shaped sectors 20' having a radial width 22', which may be trimmed after assembly into an annular preform or even after carbonization or densification of the preform. The braid 30 in the preferred embodiment shown in Figure 3 is obtained by collapsing or flattening a straight tubular braid. In addition to the braiding members 31 which extend in helical paths relative to the lengthwise direction of the braid 30, a system of longitudinal members 34 extending in the lengthwise direction of the braid is introduced into the braid as it is formed. These longitudinal members 34 may be referred to as "unidirectionals". These unidirectionals 34 improve the dimensional stability as well as the tensile strength, compressive strength and moduli, and fiber volume of the tri-directional fabric. Unidirectionals 34 are introduced from stationary guide eyes in the braiding machine such that the unidirectionals will lie straight (without crimp) parallel to the braid axis 33 (longitudinal direction of the braid) while the helical braid members 31 introduced by the braiding machine carriers pass over and under the unidirectionals as the braided fabric 30 is formed. Straight braid 30 inherently has greater lateral stability than the unidirectional "fabric" of Lawton et al. Straight braid 30 may be needlepunched prior to cutting sectors 20 therefrom to provide even greater dimensional stability of the braid itself and the sectors to be cut therefrom.

[0025] Forming some of the braid members and/or unidirectionals of different materials than are used for the remainder of the members forming the braid may benefit final mechanical or other properties, e.g. vibration damping, of the needlepunched and densified structure. Such materials could include other carbon-based and/or ceramic-based fibers. The braiding members and/or unidirectionals may be formed of staple fibers.

[0026] In the embodiment shown in Figure 4, the preform disk 40 comprises one or more helical turns 43 symmetrical about axis 44 of a fibrous tape 41 previously formed of arcuate sectors 20 joined end to end, e.g. by sewing with thread 42. The radial width of the tape 41 generally corresponds to the radial distance 24 between the inner periphery 14 and the outer periphery 16 of the flat annulus. The included angle of each sector 20 is such that the radial joints 45 of adjacent layers each formed of otherwise identical sectors are not aligned, e. g. sixty-seven degrees. The helical turns 43 of tape 41 are needlepunched to join them together. When finished, preform disk 40 is similar in appearance to that of friction disk 10 illustrated in Figure 1. One or more additional helically wound tapes (not shown in Figure 4) of similar or dissimilar construction, e. g. of continuous helical braid, may be interleaved with fibrous tape 41 to form a flat, hollow annular structure having a plurality of interleaved filamentary layers. The layers are joined by needlepunching which displaces filaments perpendicularly relative to the faces of the layers to cross-link the layers into an assembly. The longitudinal axis 46 of one of the groups of the filaments 12 in each sector 20 is disposed chordally relative to the arc of each respective sector and tangentially relative to the annular shaped structure 40. Also shown in Figure 4 in ghost lines is trapezoidal sector 20' which may be trimmed to the arcuate shape of sector 20 after manufacture of tape 41 or preform disk 40.

[0027] Having reference to Figure 5, a sheet or strip of multidirectional fabric such as crosslapped fabric 50 is shown. Fabric 50 is formed in known manner by needling together unidirectional webs of side by side filaments which webs are superposed such that the filaments of any unidirectional web forming the fabric cross at an angle to the filaments of any other unidirectional web forming the fabric. In the preferred embodiment illustrated, the fabric 50 consists of three layers of unidirectional webs and the angle of crossing of the filaments of any web is about sixty degrees relative to any other web forming the fabric 50. It is also possible to produce a suitable fabric using crossing layers, one of which is of parallelised staple fibers from a carding machine. Such carded layer may be formed from offcut waste fiber.

[0028] As shown in Figure 6, a preform 60 having an axis of symmetry 66 is made from two helically wound tapes 61, 62 of dissimilar construction. Turns 61 of a tape of continuous helical braid, may be interleaved with turns 62 of fibrous tape formed from sectors 20 to form a flat, hollow annular structure having a plurality of interleaved filamentary layers. The tape layers are joined by needlepunching which displaces filaments perpendicularly relative to the faces of the layers to cross-link the layers into an assembly.

[0029] Fibrous tape 41, as shown in Figure 4, is made by sewing together with thread 42 the radial joints 45 of the abutting circumferentially spaced ends of the adjacent sectors 20 prior to needlepunching of the stacked layers. This enables handling of a plurality of end to end abutted arcuate sectors 20 as a single helical tape portion 41 which can be guided into a rotary needlepunch loom such as that described in DE-A-2911762 to Dilo or WO-A-93/15250 to Lawton and Smith. Even when an apparatus such as that described in WO-A-93/15250 to Lawton and Smith is employed, presewing of the abutted sectors prevents separation of the abutting ends during needlepunching.

[0030] A suitable straight braid such as braid 30 of Figure 3 may be formed from a plurality of tows 12, e.g. 12k OPF tow, on a conventional tubular braiding machine (not illustrated). A simplified version of a conventional Maypole-type braiding machine and its operation are illustrated in U.S.-A- 3,007,497 to Shobert. An eminently suitable braiding machine having one hundred forty-four carriers and seventy-two unidirectional positions is available from W. STEEGER GmbH & Co. of Wuppertal, Germany.

[0031] One manner of expressing the character of a braid is in terms of picks/2.54cm (picks/inch; PPI). For a straight collapsed tubular braid formed of 12k tows of OPF and having a nominal width of 17.78cm (seven inches) when flattened, the braid has from about 2.5 to 5 picks/2.54cm (ppi). PPI is a complex function of braider speed, fibrous material pull out rate, angle of pull out and width of braid, and is empirically determined. Five PPI means that five crossovers of the members being braided occur per 2.54cm (one inch) of machine direction movement. PPI is conveniently determinable manually as the braid apparatus is empirically adjusted.

[0032] As previously stated, an optional, additional curved braid such as curved braid 61 shown in Figure 6 may be interleaved with layers formed of sectors. A curved braid may be more accurately formed by a machine rather than manually as was previously done as described in US-A-5,217,770 to Morris et al. The machinery and manufacture of curved flattened tubular braid is described in USSN 08/149,854 filed November 10, 1993 entitled CURVED BRAID APPARATUS (now US-A- 5,417,138).

[0033] One or more layers of fibrous sectors 20 are joined to one another and/or to one or more other fibrous layers superposed thereon by needlepunching. Preferably, the arcuate sectors 20 are needlepunched into a unitary preform structure as they are fed continuously onto a rotating support. This may be accomplished using a rotary needlepunch loom-such as that described in DE-A-2911762 to Dilo. This Dilo machine is provided with a needling head whose effective width corresponds to the radial extent of the fibrous strip or the arcuate sectors and preform being assembled. The apparatus described in the aforementioned patents to Lawton et al. may be employed; however the rotary receptacle need not have both inner and outer cylindrical walls to guide a continuous helical tape formed of sectors joined end to end; an inner or an outer cylindrical wall alone will suffice. The needling head of the apparatus shown in DE-A-2911762 to Dilo may be controlled programmed to avoid ovemeedling of the preform being made, which may occur at the inner periphery of the preform when using an apparatus such as that described in the aforementioned patents to Lawton et al.

[0034] If no rotary loom is available, joinder of one or more layers of fibrous sectors 20 may be accomplished by arranging the fibrous sectors into one or more superposed layers in a needle penetrable mold or jig and passing the jig and layers to be assembled to and fro through a conventional needlepunch loom. This technique is more fully described in the aforementioned patents to Lawton et al. and in U.S.-A-5,217,770 to Morris and Liew. The use of such a jig is less desirable than use of a rotary needlepunch loom because the fibrous arcuate sectors can not be fed continuously onto the jig as it is passed to and fro through a conventional reciprocal needlepunch loom such as that illustrated in U.S.-A-4,790,052 to Olry.

[0035] The resulting needlepunched structure may be thereafter subjected to CVD densification in conventional manner to produce a friction disk similar in appearance to disk 10 shown in Figure 1 having an average or bulk density of about 1.8 g/cm³. As used herein "density" is determined by weighing a specimen of known dimensions, such as that obtained by machining from the region of interest of a larger specimen, and is expressed as weight per unit volume, e.g., g/cm³.

[0036] A plurality of such densified disks made according to the invention may be machined in conventional manner and assembled to form a multidisk brake similar to that shown and described in any of U.S.-A-4,018,482; 4,878,563; and 4,613,017.

[0037] Recycled or virgin OPF staple may be used in the manufacture of yams to be formed into the fabric or fabrics to be used in manufacture of shaped filamentary structures of the invention.

[0038] It is preferred that the tows be of PAN fiber in its oxidized state (OPF) when subjected to all textile processes described herein. While it may be possible to produce suitable preform disks out of greige PAN fiber and thereafter oxidize such preforms in a batch method as opposed to the continuous oxidation method employed in the manufacture of oxidized PAN fiber, this is not deemed most economical, particularly because prior to oxidation the PAN fiber does not have the desired high density nor is it able to withstand the high temperature of the furnace cycles desired to be employed subsequent to formation of the preform disk.

[0039] While the invention has been described with reference to the use of tow, it is within the invention to use yam formed of continuous filaments or staple fibers or blends of these in place of tow for any of the braiding members and any of the multidirectionals.

Claims

1. A method of making a multi-layered annular shaped fibrous structure (10, 40) having a radius and a thickness comprising the steps of: forming a multidirectional fabric (30, 50) having filaments (12) extending in at least two directions; cutting arcuate or trapezoidal sectors (20, 20') of an annular shape from said multidirectional fabric, each sector having a radial width (22, 22') generally corresponding to the radial width (24) of the fibrous structure to be formed; assembling the sectors (20, 20') in contiguous relationship to form an annular layer (26) having a radial width (22, 22') generally corresponding to the radial width (24) of the fibrous structure to be formed; providing a stack (29) of thus formed layers (26) of fibrous material, one layer on top of another; and needlepunching the stacked layers (26) to produce cross-linking of the layers (26) by filaments (15) displaced out of the layers (26) and extending in a direction generally perpendicular to the faces (17, 18) of the layers (26).

2. The method of claim 1, wherein the multidirectional fabric (30, 50) has filaments (12) extending in three directions generally parallel to the plane defined by the fabric.

3. The method of claim 2, in which the longitudinal axis (46) of one of the groups of the filaments (12) in each sector is disposed tangentially relative to the annular shaped structure (10, 40).

4. The method of claim 2, in which the longitudinal axis (46) of one of the groups of the filaments in each sector (20) is disposed chordally relative to the arc of that sector.

5. The method of claim 1, in which each of the sectors (20) is substantially identical.

6. The method of claim 1, in which the ends of the sectors (20) forming an annular layer (26) are offset circumferentially relative to the ends of the sectors forming an immediately adjacent layer (26).

7. The method of claim 1, further comprising forming said sectors (20, 20') by cutting from a braided fabric (30).

8. The method of claim 7, further comprising providing a flattened straight tubular braid (30) having undirectionals (34), the braid having a width (35) generally corresponding the radial width (22, 22') of the sectors (20, 20') to be formed.

9. The method of claim 1, further comprising forming a helical tape (41) by joining end to end sectors (20, 20') cut from one of braided (30) and crosslapped needlepunched fabrics (50) and needling stacked turns (43) of the tape.

10. The method of claim 9, wherein the sectors (20, 20') forming the tape (41) are joined end to end by sewing (42):

11. The method of claim 1, further comprising forming the multidirectional fabric in the shape of a helical tape (70) by joining a first layer (71) of end to end abutted sectors (20) cut from fibrous material selected from the group consisting of a needlepunched layer of unidirectional filaments, braided fabrics and crosslapped needlepunched fabrics with a second layer (72) of end to end abutted sectors (20) cut from fibrous material selected from the group consisting of a needlepunched layer of unidirectional filaments, braided fabrics and crosslapped needlepunched fabrics, by needlepunching the first and second layers (71, 72) forming the tape (70) and needling stacked turns of the tape.

12. The method of claim 11, wherein the tape (70) is formed by needling together two coextensive layers (71, 72) each formed from sectors (20), the joints formed by the abutted ends of the first layer (71) being staggered relative to the joints formed by the abutted ends of the sectors of the second layer (72) forming the tape.

13. The method of claim 1, further comprising forming the multidirectional fabric in the shape of a helical tape (80) by arranging sectors (81) cut from fibrous material selected from the group consisting of a needlepunched layer of unidirectional filaments, braided fabrics and crosslapped needlepunched fabrics in partially overlapping relationship with opposite ends of each sector (81) at opposite faces (82, 83) of the tape (80) and needlepunching the arranged sectors (81) forming the tape (80) and needlepunching stacked turns of the tape (80).

14. The method of claim 1, further comprising forming the sectors (20, 20') by cutting from a crosslapped needlepunched fabric (50) that is formed by needling together unidirectional webs of side by side filaments which webs are superposed such that the filaments of any unidirectional web forming the fabric cross at an angle to any other unidirectional web forming the fabric.

15. The method of claim 14, wherein the angle of crossing of the filaments of any web is about 60 degrees relative to any other web forming the crosslapped needlepunched fabric.

16. The method of claim 1, further comprising the steps of stacking at least one layer (62) formed of arcuate sectors (20) formed from a multidirectional fabric with an additional fibrous layer (61).

17. The method of claim 16, wherein said additional fibrous layer (61) is formed of braided tape.

18. The method of claim 1, further comprising forming a flat hollow annulus (40) by helically winding a fibrous tape (41) formed of arcuate or trapezoidal sectors (20, 20') assembled end to end, the radial width (45) of the tape generally corresponding to the radial distance (24) between the inner periphery (14) and the outer periphery (16) of the flat annulus.

19. The method of claim 1, wherein the sectors are formed from the group consisting of PAN fibers including OPF, carbon fibers, graphite fibers, ceramic fibers, precursors of carbon fibers and precursors of ceramic fibers, and mixtures of these.

20. The method of claim 1, further including binding together the cross-linked layers by a matrix selected from the group consisting of carbon, ceramic, precursor of carbon, precursor of ceramic, and mixtures of these.

21. The method of claim 1, further comprising forming said sectors (20) by cutting from a straight braided filamentary tape (30) having a width (35) generally corresponding to the width (22) of the sectors (20) to be formed, and superposing at least one filamentary layer (61) on said annular layer (26), and needlepunching the stacked layers (20,61) to produce crosslinking of the layers (26,61) by filaments (15) displaced out of the layers (26,61) and extending in a direction generally perpendicular to the faces (17,18) of the layers (26,61).

22. The method of any of claims 1 to 21, in which the multi-layered annular shaped fibrous structure is a flat annulus having an inner periphery (14) and an outer periphery (16).

23. A flat annular multi-layered fibrous structure manufactured according to anyone of claims 1 to 22 (10,40,60,70,80) having a radius and a thickness comprising a stack (29) of layers (26) of fibrous material, one layer on top of another, that are cross-linked to one another by filaments (15) displaced out of the layers (26) so as to extend in a direction generally perpendicular of the faces (17,18) of the layers (26), the layers (26) being formed from arcuate or trapezoidal sectors (20,20') of an annular shape from a multidirectional fabric (30,50) having filaments (12) that extend in at least two directions, each sector having a radial width (22,22') generally corresponding to the radial width (24) of the fibrous structure; the sectors (20,20') being in contiguous or overlapping relationship to form an annular or helical layer (26,41,70,80) having a radial width (22,22',45) generally corresponding to the radial width (24) of the fibrous structure.

24. The structure of claim 23, further including a matrix selected from the group consisting of carbon, ceramic, precursor of carbon, precursor of ceramic, and mixtures of these binding together the cross-linked layers.

25. The structure of claim 24 in the form of a friction disc.

Ansprüche

1. Verfahren zur Herstellung einer mehrschichtigen ringförmigen faserigen Struktur (10,40), die einen Radius und eine Dicke aufweist, mit den Schritten: Bildung eines multidirektionalen Textilproduktes (30,50), das Filamente (12) aufweist, die sich in mindestens zwei Richtungen erstrecken; Schneiden bogenförmiger oder trapezförmiger Sektoren (20, 20') einer Ringform aus dem multidirektionalen Textilprodukt, wobei jeder Sektor eine radiale Breite (22,22') hat, die im wesentlichen der radialen Breite (24) der zu bildenden faserigen Struktur entspricht; Aneinanderlegen der Sektoren (20,20') zur Bildung einer ringförmigen Schicht (26), die eine radiale Breite (22,22') hat, die im wesentlichen der radialen Breite (24) der zu bildenden faserigen Struktur entspricht; Bilden eines Stapels (29) aus derart gebildeten Schichten (26) faserigen Materials, wobei eine Schicht über der anderen angeordnet wird; und Vernadeln der gestapelten Schichten (26), um eine Vernetzung der Schichten (26) durch Filamente (15) zu erzeugen, die aus den Schichten (26) herausragen und sich in einer Richtung erstrecken, die im wesentlichen senkrecht zu den Stirnseiten (17,18) der Schichten (26) verläuft.

2. Verfahren gemäß Anspruch 1, worin das multidirektionale Textilprodukt (30,50) Filamente (12) aufweist, die sich in drei Richtungen erstrecken, welche im wesentlichen parallel zu der durch das Textilprodukt definierten Ebene verlaufen.

3. Verfahren gemäß Anspruch 2, worin die Längsachse (46) eines Filaments der Gruppen von Filamenten (12) in jedem Sektor in bezug auf die ringförmige Struktur (10,40) tangential angeordnet ist.

4. Verfahren gemäß Anspruch 2, worin die Längsachse (46) eines Filaments der Gruppen von Filamenten in jedem Sektor (20) in bezug auf den Bogen des Sektors sehnenförmig angeordnet ist.

5. Verfahren nach Anspruch 1, worin sämtliche Sektoren (20) im wesentlichen identisch sind.

6. Verfahren nach Anspruch 1, worin die Enden der eine ringförmige Schicht (26) bildenden Sektoren (20) in bezug auf die Enden der Sektoren, welche eine unmittelbar benachbarte Schicht (26) bilden, in Umfangsrichtung gegeneinander versetzt sind.

7. Verfahren nach Anspruch 1, ferner mit dem Bilden der Sektoren (20,20') durch Schneiden aus einem geflochtenen Textilprodukt (30).

8. Verfahren nach Anspruch 7, ferner mit der Bildung eines flachgelegten, geraden, rohrförmigen Geflechts (30) mit unidirektionalen Strukturen (34), wobei das Geflecht eine Breite (35) hat, die im wesentlichen der radialen Breite (22,22') der zu bildenden Sektoren (20,20') entspricht.

9. Verfahren gemäß Anspruch 1, ferner mit der Bildung eines schraubenlinienförmigen Bandes (41) durch Ende-an-Ende-Verbinden von Sektoren (20,20'), die aus einem der geflochtenen (30) und gekreuzt übereinanderliegenden vernadelten Textilprodukte (50) ausgeschnitten wurden, und Vernadeln von gestapelten Windungen (43) des Bandes.

10. Verfahren gemäß Anspruch 9, worin die das Band (41) bildenden Sektoren (20,21) durch Nähen (42) Ende-an-Ende verbunden werden.

11. Verfahren gemäß Anspruch 1, ferner mit der Bildung eines multidirektionalen Textilprodukts in Form eines schraubenlinienförmigen Bandes (70) durch Verbinden einer ersten Schicht (71) von aneinanderstoßenden Sektoren (20), die aus faserigem Material geschnitten sind, das aus der Gruppe gewählt ist, die eine vernadelte Schicht von unidirektionalen Filamenten, geflochtene Textilprodukte und gekreuzt übereinanderliegende vernadelte Textilprodukte enthält, mit einer zweiten Schicht (72) von aneinanderstoßenden Sektoren (20), die aus faserigem Material geschnitten sind, das aus der Gruppe gewählt ist, die eine vernadelte Schicht von unidirektionalen Filamenten, geflochtene Textilprodukte und gekreuzt übereinanderliegende vernadelte Textilprodukte enthält, durch Vernadelung der das Band (70) bildenden ersten und zweiten Schichten (71,72) und Vernadelung gestapelter Windungen des Bandes.

12. Verfahren nach Anspruch 11, worin das Band (70) durch Vernadelung zweier koextensiver Schichten (71,72) gebildet wird, die jeweils aus Sektoren (20) gebildet werden, wobei die durch die angrenzenden Enden der ersten Schicht (71) gebildeten Verbindungen in bezug auf die Verbindungen versetzt angeordnet sind, die durch die angrenzenden Enden der Sektoren der zweiten Schicht (72) gebildet werden, welche das Band bilden.

13. Verfahren gemäß Anspruch 1, worin ferner das multidirektionale Textilprodukt in Form eines schraubenlinienförmigen Bandes (80) gebildet wird, indem Sektoren (81), die aus faserigem Material geschnitten sind, das aus der Gruppe gewählt ist, die eine vernadelte Schicht von unidirektionalen Filamenten, geflochtene Textilprodukte und gekreuzt übereinanderliegende vernadelte Textilprodukte enthält, in einer partiell überlappenden Beziehung zu den gegenüberliegenden Enden jedes Sektors (81) an gegenüberliegenden Stirnseiten (82,83) des Bandes (80) angeordnet werden, die das Band (80) bildenden angeordneten Sektoren (81) vernadelt werden und gestapelte Windungen des Bandes (80) vernadelt werden.

14. Verfahren gemäß Anspruch 1, worin ferner die Sektoren (20,20') durch Schneiden aus einem gekreuzt übereinanderverlaufenden vernadelten Textilprodukt (50) gebildet werden, das durch Vernadelung unidirektionaler Bahnen nebeneinander angeordneter Filamente gebildet wird, wobei die Bahnen derart übereinandergelegt werden, daß die Filamente jeder das Textilprodukt bildenden, unidirektionalen Bahn jede andere das Textilprodukt bildende, unidirektionale Bahn unter einem Winkel kreuzen.

15. Verfahren nach Anspruch 14, worin der Kreuzungswinkel der Filamente jeder Bahn in bezug auf jede andere das gekreuzt übereinanderverlaufende vernadelte Textilprodukt bildenden Bahn ungefähr 60 Grad beträgt.

16. Verfahren nach Anspruch 1, ferner mit dem Schritt des Stapelns mindestens einer Schicht (62), die aus bogenförmigen Sektoren (20) gebildet wird, welche aus einem multidirektionalen Textilprodukt mit einer zusätzlichen faserigen Schicht (61) gebildet werden.

17. Verfahren nach Anspruch 16, worin die zusätzliche faserige Schicht (61) aus geflochtenem Band gebildet wird.

18. Verfahren nach Anspruch 1, bei dem ferner ein flacher Hohlring (40) durch schraubenlinienförmiges Wickeln eines faserigen Bandes (41) gebildet wird, das aus bogenförmigen oder trapezförmigen Sektoren (20,20') gebildet ist, die aneinanderstoßend zusammengefügt sind, wobei die radiale Breite (45) des Bandes im wesentlichen dem radialen Abstand (24) zwischen dem Innenumfang (14) und dem Außenumfang (16) des flachen Rings entspricht.

19. Verfahren nach Anspruch 1, worin die Sektoren aus der Gruppe gebildet werden, die PAN-Fasern einschließlich OPF, Kohlenstoff-Fasern, Graphitfasern, Keramikfasern, Vorstufen von Kohlenstoff-Fasern und Vorstufen von Keramikfasern und Mischungen derselben enthält.

20. Verfahren nach Anspruch 1, worin ferner die vernetzten Schichten durch eine Matrix gebildet werden, die aus der Gruppe gewählt ist, welche Kohlenstoff, Keramik, eine Kohlenstoff-Vorstufe, eine Keramik-Vorstufe und Mischungen derselben enthält.

21. Verfahren gemäß Anspruch 1, bei dem ferner die Sektoren (20) durch Schneiden aus einem geraden, geflochtenen, filamentartigen Band (30) mit einer Breite (35) gebildet werden, die im wesentlichen der Breite (22) der zu bildenden Sektoren (20) entspricht, und mindestens eine filamentartige Schicht (61) über der ringförmigen Schicht (26) angeordnet wird und die gestapelten Schichten (20,61) vernadelt werden, um eine Vernetzung der Schichten (26,61) durch Filamente (15) zu erzeugen, die aus den Schichten (26,61) herausragen und sich in einer Richtung erstrecken, die im wesentlichen senkrecht zu den Stirnseiten (17,18) der Schichten (26,61) verläuft.

22. Verfahren gemäß einem der Ansprüche 1 bis 21, worin die mehrschichtige ringförmige faserige Struktur ein flacher Ring ist, der einen Innenumfang (14) und einen Außenumfang (16) hat.

23. Flache ringförmige mehrschichtige faserige Struktur (10,40,60,70,80), hergestellt nach einem der Ansprüche 1 bis 22, mit einem Radius und einer Dicke, wobei die Struktur einen Stapel (29) übereinander angeordneter Schichten (26) aus faserigem Material aufweist, die durch Filamente (15) miteinander vernetzt sind, welche aus den Schichten (26) derart herausragen, daß sie sich in einer im wesentlichen senkrecht zu den Stirnseiten (17,18) der Schichten (26) verlaufenden Richtung erstrecken, wobei die Schichten (26) aus bogenförmigen oder trapezartigen Sektoren (20,20') einer Ringform aus einem multidirektionalen Textilprodukt (30, 50) gebildet sind, das Filamente (12) aufweist, die sich in mindestens zwei Richtungen erstrecken, wobei jeder Sektor eine radiale Breite (20, 22') hat, die im wesentlichen der radialen Breite (24) der faserigen Struktur entspricht; wobei die Sektoren (20,20') in einer einander angrenzenden oder überlappenden Beziehung stehen, um eine ringförmige oder schraubenlinienförmige Schicht (26,41,70,80) zu bilden, die eine radiale Breite (22,22',45) hat, welche im wesentlichen der radialen Breite (24) der faserigen Struktur entspricht.

24. Struktur gemäß Anspruch 23, ferner mit einer die vernetzten Schichten verbindenden Matrix, die aus der Gruppe gewählt ist, welche Kohlenstoff, Keramik, eine Kohlenstoff-Vorstufe, eine Keramik-Vorstufe und Mischungen derselben enthält.

25. Struktur gemäß Anspruch 24 in der Form einer Bremsscheibe.

Revendications

1. Procédé pour fabriquer une structure fibreuse (10, 40), de forme annulaire, multi-couche, ayant un rayon et une épaisseur, comportant les étapes consistant à : former un tissu multi-directionnel (30, 50) comportant des filaments (12) qui s'étendent dans au moins deux directions ; découper des secteurs arqués ou trapézoïdaux (20, 20') de forme annulaire à partir dudit tissu multi-directionnel, chaque secteur ayant une largeur radiale (22, 22') qui correspond généralement à la largeur radiale (24) de la structure fibreuse à former ; assembler les secteurs (20, 20') selon une relation de contiguïté de manière à former une couche annulaire (26) ayant une largeur radiale (22, 22') qui correspond d'une manière générale à la largeur radiale (24) de la structure fibreuse à former ; constituer un empilement (29) de couches (26) de matériau fibreux ainsi formées, une couche au-dessus d'une autre ; et aiguilleter les couches (26) empilées afin de produire une réticulation des couches (26) grâce à des filaments (15) déplacés hors des couches (26) et s'étendant dans une direction généralement perpendiculaire aux faces (17, 18) des couches (26).

2. Procédé selon la revendication 1, dans lequel le tissu multi-directionnel (30, 50) comporte des filaments (12) qui s'étendent dans trois directions généralement parallèles au plan défini par le tissu.

3. Procédé selon la revendication 2, dans lequel l'axe longitudinal (46) de l'un des groupes de filaments (12), dans chaque secteur, est disposé tangentiellement par rapport à la structure de forme annulaire (10, 40).

4. Procédé selon la revendication 2, dans lequel l'axe longitudinal (46) de l'un des groupes de filaments, dans chaque secteur (20), est disposé à la corde par rapport à l'arc de ce secteur.

5. Procédé selon la revendication 1, dans lequel chacun des secteurs (20) est sensiblement identique.

6. Procédé selon la revendication 1, dans lequel les extrémités des secteurs (20) formant une couche annulaire (26) sont décalées circonférentiellement par rapport aux extrémités des secteurs formant une couche (26) immédiatement adjacente;

7. Procédé selon la revendication 1, consistant, en outre, à former lesdits secteurs (20, 20') par découpe à partir d'un tissu tressé (30).

8. Procédé selon la revendication 7, consistant, en outre, à fournir un tissu tressé (30) tubulaire rectiligne aplati comportant des unidirectionnels (34), le tissu tressé ayant une largeur (35) qui correspond d'une manière générale à la largeur radiale (22, 22') des secteurs (20, 20') à former.

9. Procédé selon la revendication 1, consistant, en outre, à former une bande hélicoïdale (41) en reliant bout-à-bout les secteurs (20, 20') découpés à partir de tissu tressé (30) ou de tissus aiguilletés entrecroisés (50) et relier à l'aiguille les tours empilés (43) de la bande.

10. Procédé selon la revendication 9, dans lequel les secteurs (20, 20') formant la bande (41) sont reliés bout-à-bout par couture (42).

11. Procédé selon la revendication 1, consistant, en outre, à former le tissu multi-directionnel sous la forme d'une bande hélicoïdale (70) en reliant une première couche (71) de secteurs (20), mis bout-à-bout, découpés à partir d'un matériau fibreux choisi parmi le groupe constitué d'une couche aiguilletée composée de filaments unidirectionnels, de tissus tressés et de tissus aiguilletés entrecroisés à une seconde couche (72) de secteurs (20), mis bout-à-bout, découpés à partir d'un matériau fibreux choisi parmi le groupe constitué d'une couche aiguilletée constituée de filaments unidirectionnels, tissus tressés et de tissus aiguilletés entrecroisés, en aiguilletant les première et seconde couches (71, 72) formant la bande (70) et en reliant à l'aiguille les tours empilés de la bande.

12. Procédé selon la revendication 11, dans lequel la bande (70) est formée en reliant ensemble à l'aiguille deux couches coextensives (71, 72), formées chacune à partir de secteurs (20), les jointures formées par les extrémités mises bout-à-bout de la première couche (71) étant décalées par rapport aux jointures formées par les extrémités mises bout-à-bout des secteurs de la seconde couche (72) formant la bande.

13. Procédé selon la revendication 1, consistant, en outre, à former le tissu multi-directionnel sous la forme d'une bande hélicoïdale (80) en disposant des secteurs (81) découpés à partir d'un matériau fibreux, choisi parmi le groupe constitué d'une couche aiguilletée constituée de filaments unidirectionnels, de tissus tressés et de tissus aiguilletés entrecroisés selon une relation de chevauchement partiel avec les extrémités opposées de chaque secteur (81) au niveau de faces opposées (82, 83) de la bande (80) et aiguilleter les secteurs (81) disposés qui forment la bande (80) et aiguilleter les tours empilés de la bande (80).

14. Procédé selon la revendication 1, consistant, en outre, à former les secteurs (20, 20') par découpe à partir d'un tissu aiguilleté entrecroisé (50) qui est formé en reliant ensemble à l'aiguille des toiles unidirectionnelles de filaments agencés côte à côte, lesquelles toiles sont superposées de sorte que les filaments d'une toile unidirectionnelle quelconque formant le tissu recoupent avec un certain angle n'importe quelle autre toile unidirectionnelle formant le tissu.

15. Procédé selon la revendication 14, dans lequel l'angle d'intersection des filaments d'une toile quelconque est de l'ordre de 60 degrés par rapport à n'importe quelle autre toile formant le tissu aiguilleté entrecroisé.

16. Procédé selon la revendication 1, comportant, en outre, les étapes consistant à empiler au moins une couche (62) formée de secteurs arqués (20) formés à partir d'un tissu multi-directionnel avec une couche fibreuse (61) additionnelle.

17. Procédé selon la revendication 16, dans lequel ladite couche fibreuse (61) additionnelle est formée d'une bande tressée.

18. Procédé selon la revendication 1, consistant, en outre, à former un anneau creux plat (40) en enroulant en hélice une bande fibreuse (41) formée de secteurs arqués ou trapézoïdaux (20, 20') assemblés bout-à-bout, la largeur radiale (45) de la bande correspondant d'une manière générale à la distance radiale (24) existant entre la périphérie intérieure (14) et la périphérie extérieure (16) de l'anneau plat.

19. Procédé selon la revendication 1, dans lequel les secteurs sont formés à partir dû groupe constitué de fibres de polyacrylonitrile, y compris de fibres de polyacrylonitrile oxydé, de fibres de carbone, de fibres de graphite, de fibres de céramique, de précurseurs de fibres de carbone et de précurseurs de fibres de céramique, ainsi que de leurs mélanges.

20. Procédé selon la revendication 1, consistant en outre à relier ensemble les couches réticulées par une matrice choisie parmi le groupe constitué de carbone, de céramique, de précurseur de carbone, de précurseur de céramique, ainsi que de leurs mélanges.

21. Procédé selon la revendication 1, consistant, en outre, à former lesdits secteurs (20) par découpe à partir d'une bande filamentaire tressée rectiligne (30) ayant une largeur (35) qui correspond d'une manière générale à la largeur (22) des secteurs (20) à former, et à superposer au moins une couche filamentaire (61) sur ladite couche annulaire (26), et aiguilleter les couches empilées (20, 61) afin de produire une réticulation des couches (26, 61) grâce à des filaments (15) déplacés hors des couches (26, 61) et s'étendant dans une direction généralement perpendiculaire aux faces (17, 18) des couches (26, 61).

22. Procédé selon l'une quelconque des revendications 1 à 21, dans lequel la structure fibreuse de forme annulaire multi-couche est un anneau plat ayant une périphérie intérieure (14) et une périphérie extérieure (16).

23. Structure fibreuse multi-couche annulaire plate (10, 40, 60, 70, 80) fabriquée selon l'une quelconque des revendications 1 à 22, ayant un rayon et une épaisseur comportant un empilement (29) de couches (26) constituées d'un matériau fibreux, une couche au-dessus d'une autre, qui sont réticulées les unes aux autres par des filaments (15) déplacés hors des couches (26) de manière à s'étendre dans une direction généralement perpendiculaire aux faces (17, 18) des couches (26), les couches (26) étant formées à partir de secteurs arqués ou trapézoïdaux (20, 20') de forme annulaire à partir d'un tissu multi-directionnel (30, 50) ayant des filaments (12) qui s'étendent dans au moins deux directions, chaque secteur ayant une largeur radiale (22, 22') qui correspond d'une manière générale à la largeur radiale (24) de la structure fibreuse ; les secteurs (20, 20') étant agencés selon une relation de contiguïté ou de chevauchement pour former une couche annulaire ou hélicoïdale (26, 41, 70, 80) ayant une largeur radiale (22, 22', 45) qui correspond d'une manière générale à la largeur radiale (24) de la structure fibreuse.

24. Structure selon la revendication 23, comportant, en outre, une matrice choisie parmi le groupe constitué de carbone, de céramique, de précurseur de carbone, de précurseur de céramique, ainsi que de mélanges de ces liants, en association avec les couches réticulées.

25. Structure selon la revendication 24 se présentant sous la forme d'un disque de friction.

Drawing